Thermal Response Test (TRT)

Thermal Response Test (TRT)

Thermal Response Test (TRT) represents a method of evaluating the thermal properties of the subsoil, the most important of which are:

  1. Tground – Undisturbed ground temperature
  2. λ- Borehole Thermal conductivity
  3. R- Borehole Thermal Resistance

Thermal Response Test Equipment

There are two modes of operation of the equipment in the thermal response test to shed or extract heat from or to the borehole heat exchanger under test. This is accomplished by circulating a fluid through the borehole that is warmer during the injection process and cooler during the extraction process than the surrounding soil. The image below shows a classic equipment layout (TRT).

Operating principle Thermal Response Test

First of all , the undisturbed soil temperature is determined, by recording the temperature at the surface of the borehole or by evaluating the temperature of the liquid circulating in the geoexchanger before activating the cooling or heating. The term thermal response is defined as the measured change in the average temperature of the inlet and outlet temperatures of the fluid over time. Superimposed temperature variations are usually dependent on changing ambient air temperature or corresponding variations in power supply to the electric heater and circulation pump. Therefore air temperature and power consumption are often measured to separate such disturbances during evaluation. It is worth noting that several equipment compensate for these fluctuations by using a control to provide constant power.

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